This study estimated energy, environmental and consumer economic impacts of U.S. federal residential energy efficiency standards that became effective in the 1988-2001 period or will take effect by the end of 2007. These standards have been the subject of in-depth analyses conducted as part of DOE's standards rulemaking process. This study drew on those analyses, but updated certain data and developed a common framework and assumptions for all of the products in order to estimate realized impacts and to update projected impacts. We estimate that the considered standards will reduce residential primary energy consumption and CO2 emissions in 2020 by 8% compared to the levels expected without any standards. They will save a cumulative total of 34 quads by 2020, and 54 quads by 2030. The estimated cumulative net present value of consumer benefit amounts to $93 billion by 2020, and grows to $125 billion by 2030. The overall benefit/cost ratio of cumulative consumer impacts is 2.45 to 1. While the results of this study are subject to a fair degree of uncertainty, we believe that the general conclusions — DOE's energy efficiency standards save significant quantities of energy (and associated carbon emissions) and reduce consumers' net costs — are robust.